The present invention relates to an apparatus for dispensing liquids and more particularly to such apparatus having a reliable liquid product metering system of simple and economical construction.
Known product dispensers of various types are found in a wide range of structures, both simple and complex, having a liquid product metering capability. One such dispenser for controllably applying a liquid herbicide to noxious weeds via a contact pad is described in U.S. Pat. No. 5,555,673 Smith wherein, an elongated tube that functions as a handle and herbicide reservoir having a distal end normally closed by a valve assembly extending therefrom is held reciprocally captive within a short dispensing cylinder coupled to the pad. Reciprocal travel of the tube to open and close the valve is limited by a pair of stop screws extending from the cylinder into an annular channel formed by a pair of sleeves disposed in spaced relation on the distal end of the tube. Tube movement is thus limited by the distance traversed by the screws between the side walls of the channel.
Although simple in design, the dispenser is expected to be problematic due to excessive impact wear between the annular sleeves and stop screws. Furthermore, accurate metering of herbicide is not achieved since the quantity released at a given time is not predetermined but depends rather on the period that the valve remains open.
Another example of a dispenser for controlled release of a liquid is seen in U.S. Pat. No. 4,608,045 Fretwell which discloses an applicator for impressing ink brands or medicaments on animals. A short handle includes a chamber for liquids communicating with a base that is configured in a predetermined pattern through which a liquid product stored in the handle is applied to an animal. The handle includes a neck portion that is reciprocally captive within a short cylinder screwed into the base.
A valve assembly comprises a plunger valve in the distal end of the neck and a foot valve in the distal end of the cylinder, the valves being spaced apart to define a chamber of variable volume. Advancing the neck into the cylinder brings the valves together and compresses air in the chamber which expels product under pressure through the foot valve into the base and therethrough onto the animal. Return of the neck by a coil spring separates the valves and expands the chamber volume, resulting in a partial vacuum that opens the plunger valve and admits a predetermined quantity of product into the chamber for subsequent dispensing.
Incursion of the neck into the cylinder is controlled by a threaded sleeve positioned along the neck to adjust the distance between the distal end of the sleeve and the base. The chamber volume is thus varied which controls the partial vacuum pressure applied to the plunger valve and the amount of product drawn into the chamber.
Although the Fretwell applicator appears well adapted to serve as a branding and medicament application device with means for accurately metering out a product, its overall structure is complex in design and therefore not well suited to economical manufacture.
Having regard to the aforedescribed problems pertaining to the economical manufacture of a liquid product dispenser, and related problems associated with controllably metering out the product, a principal provision of the invention is a general purpose liquid product dispenser of reliable and cost-effective construction.
A further provision of the invention is a liquid product dispenser employing a simple liquid product metering system that is easily adjusted in the field.
Yet another provision of the invention is an adjustable liquid product metering system that includes a resilient cushion to absorb impact forces incurred in normal dispenser operation.
The problems associated with the prior art may be substantially overcome and the foregoing provisions achieved by recourse to the invention which, in one aspect thereof, relates to a dispenser, comprising in combination, a liquid product container having a closed end and an open end coterminous with an outlet conduit, pump means comprising a spring biased pumping assembly housed in a cylindrical body portion removably inserted within the conduit into communication with the interior of the container, closure means sealingly engaging the body portion with the free end of the conduit, and a discharge tube reciprocally captive within the body portion and extending therefrom for actuating the pumping assembly and withdrawing a predetermined quantity of the product. A hollow coupler having an open end is adapted to receive the closure means and discharge tube in axially slidable relation. Stop means disposed within the coupler at a predetermined distance from the open end adjustably limits incursion of the closure means. An end wall of the coupler includes a central aperture circumscribed by a cylindrical surface that engages the free end of the discharge tube in an interference fit, permitting displacement of the closure means into abutment with the stop means that results in a corresponding incursive stroke of the discharge tube within the body portion and withdrawal of a predetermined quantity of the product in direct proportion to the length of the stroke.
Still another aspect of the invention relates to a method for controllably withdrawing a predetermined quantity of product carried in a dispenser that comprises, in combination, a liquid product container having a closed end and an open end coterminous with an outlet conduit, pump means comprising a spring biased pumping assembly housed in a cylindrical body portion removably inserted within the conduit into communication with the interior of the container, closure means sealingly engaging the body portion with the free end of the conduit, a discharge tube reciprocally captive within the body portion and extending therefrom for actuating the pumping assembly, and a hollow coupler having an open end. The method comprises the steps of, inserting the closure means and discharge tube into the coupler in axially slidable relation, providing stop means within the coupler at a predetermined distance from the open end to adjustably limit incursion of the closure means, providing an end wall in the coupler with a central aperture therein circumscribed by a cylindrical surface engaging the free end of the discharge tube in an interference fit, displacing the closure means into abutment with the stop means to effect a corresponding incursive stroke of the discharge tube within the body portion, and withdrawing a predetermined quantity of the product in direct proportion to the length of the stroke.